Traditional approaches to illuminating an instrument cluster include positioning a light housing (alternately referred to as a light box) and a diffuser behind the instrument cluster, thereby illuminating the instrument cluster. The light housing contains a light guide that redirects light from a light source behind the light housing, such as an LED, throughout the light housing. As the light travels along the light guide, the light escapes the light guide at various points thereby distributing the light throughout the light housing. A diffuser is placed covering a forward facing opening of the light housing and further diffuses the light escaping from the light guide.
Due to the nature of light guides, a typical light housing diffuser includes bright portions and dim portions, with the brightest portions of the diffuser being closest to the light source, and the dimmest portions of the diffuser being farthest from the light source. In order to compensate for the increased brightness nearest the light source, a darkening color is screen printed on the diffuser nearest the light source to reduce the light allowed to pass through the diffuser. The printing allows for a more even distribution of the light passing through the diffuser, but at the cost of a decreased total magnitude of light.
An alternate solution for removing or reducing the bright areas has been a distribution of micro lenses on the top (exterior facing) surface of the diffuser. The micro lenses provide a similar effect and distribute the light more evenly. As with the screen printing, the micro-lenses also reduce the magnitude of light passing through the diffuser resulting in an overall dimmer lighting.